1. Field of the Invention
This invention relates to a method and system for machining a part having a contoured surface and, more particularly, to a method and apparatus for repairing cracks and holes in a vane of a vane segment from a nozzle ring of a gas turbine engine and the like by generating a machining contour profile of the vane using a series of data points from the original surface of the vane.
2. Description of Related Art
In the aircraft industry, various components of the aircraft have to be periodically repaired. For example, high pressure turbine vanes often become cracked and corroded. In order to return the vanes to an operable condition which approximated their original shape, the vanes were heated to approximately 1400.degree. F. and placed into a die under pressure and allowed to cool. The vanes were then typically processed through a fluoride ion cleaning cycle and then vacuum cleaned through a heat treat cycle. In a "clean-room" environment, a braze alloy was manually applied to cracks and pits using a hypodermic needle. The vanes were then processed through a braze operation in a heat treat furnace.
The braze alloy typically had peaks of up to 0.030 inch high or higher wherever the braze alloy was applied. The outer surface of the vane had to be machined to approximately 0.005 inch above the original surface.
In the past, the vane could not be machined in accordance with its original dimensions because the configuration of the vane would change due to thermal stress through normal use. It was also difficult to machine the vane because the underlying surface contour was not known. Accordingly, the peaks of braze alloy material had to be manually removed using high speed pencil grinders which use small grinding wheels or carbide burrs. This manual process is slow and time consuming.
Another disadvantage of current methods for machining the vanes is that it is difficult to obtain the proper vane shape, and an inexperienced operator can easily grind off more braze alloy material than necessary, thereby leaving the part slightly weaker than before. This also can detrimentally impact the number of times the vane can be repaired.